The present invention relates to an improved subcutaneous valve intended for therapeutic applications and to a new and improved device for externally setting it which makes it possible to alter a passage or distribution of liquid into implanted systems or prostheses through the cutaneous tissues.
Among the therapeutic applications of the valve according to the invention, mention may be made of the treatment of hydrocephalus which consists in diverting the cerebrospinal fluid contained in the ventricles of the cranial cavity towards some other resorption site.
A known subcutaneous valve is described in French Patent No. 81 05389, corresponding to U.S. Pat. No. 4,443,214, of the Applicant Company.
Such prior art valve includes a body consisting of a substantially cylindrical and flat internal cheer, an inlet pipe and a drain pipe, formed in the lateral wall of the said chamber and capable of being connected respectively to a catheter for supplying a fluid and a catheter for draining a fluid away, a rotor able to turn in the said chamber about its central axis, a non-return valve, consisting of a ball and of a cone-shaped seat formed at the inner end of the inlet pipe, a semicircular leaf spring fixed to the said rotor, parallel to the lateral wall of the chamber and compressing the ball into its seat so as to regulate, and if appropriate block, the passage of fluid into the chamber via the inlet pipe, two micro-magnets mounted in the rotor and arranged on either side of the central axis of the chamber and means for locking the rotor in a determined position, the locking means including a lug projecting from one end of the rotor and cavities for accommodating the lugs, which cavities are formed in a circle in the lateral wall of the valve body, the said cavities having a shape desired to retain the said lugs.
Insofar as the prior art rotor includes micro-magnets, it is possible, by means of a magnet placed vertically in line with the valve, to drive the rotor in rotation through the wall of the valve and the cutaneous tissue covering it when the valve is implanted. It is thus possible to set the rotor into its various locked positions from a distance and from outside, and consequently to modify the operating throughput and pressure of the valve.
However, this type of valve with a magnetic rotor exhibits the drawback that its setting can be altered under the action of a strong external magnetic or electromagnetic field, such as the one encountered in nuclear magnetic resonance imaging.
This drawback is very uncomfortable for wearers of valves of the abovementioned type who have to have their valve reset after each examination employing techniques such as nuclear magnetic resonance imaging.